1. Field of the Invention
The present invention relates to the structure of a lens barrel having a rotary frame and a rectilinear guide frame which advances or retracts together with the rotary frame.
2. Description of the Related Art
A popular retractable lens barrel has such a structure that it is housed inside a camera body when not in operation, popping out of the camera body upon shooting. Further, recent retractable lens barrels typically advance or retract for a zooming operation of an optical system during shooting.
A typical structure of a lens barrel to advance or retract like those mentioned above has a driving frame, a rectilinear guide frame, and a driven frame. The driving frame is provided with a helicoid or cam. The rectilinear guide frame is displaced integrally with the driving frame in an optical axis direction to turn around the optical axis relative to the driving frame. The rectilinear guide frame has a rectilinear guide extending in the optical axis direction. The driven frame is engaged with the helicoid or cam provided in the driving frame. Further, the driven frame is engaged with the rectilinear guide provided in the rectilinear guide frame, so that the driven frame is advanced or retracted by the driving frame in the optical axis direction in such a state that it is guided by the rectilinear guide frame in the optical axis direction.
In addition, conventional lens barrels are also required to be light-tight to prevent an unwanted or stray light flux from entering the lens barrels in order not to cause flare or ghost. To this end, for example, such a structure that only either the driving frame or the rectilinear frame is exposed to the outside of the lens barrel is typically employed to prevent the unwanted light flux from entering the lens barrel.
The aforementioned conventional lens barrel structure is proposed, for example, in Japanese Patent Application Laid-Open Nos. 8-313788 and 2004-252365.